MacPherson-style strut assemblies are well known in the automotive industry. Such assemblies typically comprise a strut which extends upward from the steering knuckle of the wheel and terminates in a top mount attached to the chassis of the vehicle. The strut includes a hydraulic cylinder and a spring for absorbing movement and bounce of the vehicle. The joint between the top mount and the strut contains a strut bearing. Typically, a strut bearing includes two relatively rotatable elements, for example an upper and lower housing made of plastic or metal, provided with a bearing arranged therebetween to facilitate rotation while at the same time permitting load transmission between the elements. The bearing can include rolling elements or a synthetic resin sliding bearing arrangement, both known in the art. The lower housing typically includes a spring seat, integrally formed, to support an upper end of the strut spring.
In order to ensure proper operation of the strut bearing, particularly of the rolling elements or sliding bearing, it is necessary to protect the bearing components from pollutants such as road dust and humidity. Several arrangements may prevent intrusion of dust and contaminants into the bearing, including a labyrinth or flinger type seal arrangement between the upper and lower housing, such as that shown in U.S. Pat. No. 6,948,728. Such configurations do not provide complete sealing and may allow contamination to enter the bearing portion of the strut. Alternatively, full contact seals, having lips directed toward the upper and lower housings, respectively, can be used and provide complete sealing. However, such configurations cause high friction during operation, which is generally undesirable.
Therefore, an intermediate solution, providing improved sealing, but, limiting frictional losses is needed.